Rotary regenerative heat exchangers are well known, and an example of such heat exchanger is described in our EP-A-0599577.
The stator, often termed the rotor housing, includes means for introducing along a first path into the spaces between the radial diaphragms or vanes of the rotor, at least a first fluid which is relatively hot and gives up its heat to heat exchange media contained within those spaces, and a second path for a relatively cool fluid which passes through a different sector of the rotor to recover heat from the heat exchange media in that particular part of the heat exchanger rotor. As the rotor rotates the heated heat exchange media from the first sector passes from the first path to the second path to give up its heat to the relatively cool fluid. Often there will be additional fluid flow paths, for example in the case where the relatively hot fluid is flue gas from a combustion unit and the relatively cool fluid may comprise the combustion gas and secondary air which may pass through the heat exchanger in different sectors of the rotor housing.
In order to prevent transfer of fluid and thermal energy between the zones of differing temperature in the rotor housing or stator, particularly in the case where there may be substantial pressure differences between the fluids flowing through the rotor heat exchange media pockets in the different paths, it is necessary to provide sealing means to ensure that the pockets within the rotor forming part of one sector are sealed from the pockets of an adjacent sector. Where substantial pressure differences arise between the two adjacent pockets in such a system, the sealing effect is frequently enhanced by ensuring that the stator plate past which the seals move, and which separates the one sector from the other, seals simultaneously with two or more of the vanes or diaphragms, thereby giving an enhanced labyrinth sealing effect. However, this has the disadvantage that the dead space between adjacent sectors increases in order to allow several of the diaphragms to seal against the sector plate.